1、提权进入root

sudo -i

2、卸载composer

apt-get remove composer

3、下载composer.phar

wget https://getcomposer.org/composer.phar

4、增加可执行权限

chmod +x composer

5、加入全局命令

mv composer /usr/bin/composer

6、升级composer

composer self-update

7、退出root账户

exit

8、清除缓存

composer clear

composer使用阿里源

composer config -g repo.packagist composer https://mirrors.aliyun.com/composer/

composer取消使用阿里源

composer config -g --unset repo.packagist